Ejection issues with the gen4 G17 & G19 and possibly others that is where the "gray area" is in web chat anyways. I researched this for two days as I was looking into a G19 for my aunt. It sounds for the most part that the issues is fixed but I am still hesitant.

Good slow motion vid in this thread:
http://www.co-ar15.com/forums/showthread.php?t=45357